Model Could not be loaded issue came for some models

<?php
use Phalcon\Mvc\Model;
class DocLinks extends Model {
public $id;
public $folder_id;
public $type;
public $title;
public $priority;
public $image;
public $url;
public $created_date;
public $updated_date;

<?php
use Phalcon\Mvc\Model;
class users extends Model {
public $user_id;
public $emp_id;
public $password;
public $salt;
public $first_name;
public $midile_name;
public $last_name;
public $preferred_name;
public $created;
public $email;
public $access_level;
public $inactive;
public $updated;
public $status;
public $hire_date;
public $birth_date;
public $regular_pay_rate_code;